Generality
Tumors are pathologies characterized by rapid and uncontrolled cell proliferation. In benign tumors this proliferation is slow and limited to the site of origin, while the cells of malignant tumors have a high proliferative capacity and can invade and destroy the surrounding tissues, up to spreading to other parts of the body through the bloodstream and / or the lymphatic circulation (metastasis).
The staging of a tumor is a fundamental part in the diagnosis of the disease. In fact, the prognosis of the tumor and the type of therapy that must be adopted to treat it (surgery, chemotherapy, radiotherapy, immunotherapy, etc.) depend on the stage of the tumor.
TNM classification of malignant tumors
There are various classification methods to describe the stage at which malignant tumors are found. The most used is the TNM classification system (Tumor - Node - Metastasis). This system was first introduced in France by Pierre Denoix, between 1943 and 1952.
The TNM classification has earned great international approval, but it mostly applies to solid-type cancers. On the other hand, it is not applicable to diffuse tumors such as leukemia and has limited application in tumors such as diffuse lymphoma and ovarian cancer.
Each tumor possesses four stages, indicated - in order of increasing severity - with numbers THE, II, III And IV. To these must be added the stage 0, in the case of carcinomas in situ.
In the TNM classification, each letter indicates a parameter that describes certain characteristics of the tumor:
- Letter T.: indicates the size of the primary tumor. The value of this parameter ranges from 1 (small tumor) to 4 (large tumor). The letter T may be accompanied by the abbreviation "is"(Tis), in case the tumor is in situ. If the letter T is followed by the letter "x"(Tx) means that tumor size cannot be assessed.
- Letter N.: indicates the involvement of the lymph nodes that are in the vicinity of the tumor. The value of this parameter goes from 0 (no lymph nodes involved) to 3 (many lymph nodes involved). Again, if the letter N is followed by the letter "x"(Nx) means that the amount of lymph nodes involved cannot be determined.
- Letter M: indicates the presence of metastases. It can take the value 0 (no metastases) or value 1 (presence of metastases).
Depending on the type of tumor and where it is located, the TNM parameters take on a different meaning: for example, T2 N0 M0 is part of stage II of breast cancer, but corresponds to stage I of lung cancer.
In addition, TNM parameters can also be indicated with letters as well as numbers. An example is that of lung cancer, in which acronyms can be used to describe the type of metastasis M1a or M1b: the first indicates that the metastasis is localized to the opposite lung, the second indicates that the tumor has spread to other areas of the body.
Below is an example of lung cancer classification:
(the tumor is in situ)
T3 N0 M0
T3 N1-3 M0
T4 N0-3 M0
(when in the presence of any type of metastasis)
Degree of aggressiveness of the tumor
The degree of aggression is another parameter used to have a more detailed classification of the tumor. It provides information on the degree of cellular differentiation of the neoplasm. It is indicated with the letter "G" and takes values from 1 to 4.
Grade 1 (G1) corresponds to a well differentiated tumor, ie the cells that compose it - analyzed under a microscope - have characteristics very similar to the normal ones of the original tissue. A G1 tumor tends to grow slowly, has a low invasiveness and, if detected and treated in a timely manner, can correlate to a positive prognosis.
Grade 4 (G4) corresponds to a undifferentiated tumor, that is, the cells that constitute it differ greatly in morphological characteristics from those of normal tissues, becoming almost unrecognizable. G4 tumors tend to grow and spread rapidly.
Again, if the letter G is followed by the letter "x"(Gx) means that it is not possible to determine the degree of differentiation.
Well-differentiated tumors are the least aggressive, because the tumor cells still possess similar characteristics to the healthy ones of the tissue in which they developed; conversely, a low degree of differentiation corresponds to a "high aggressiveness.
Analysis to determine the stage of the tumor
To determine the stage of a tumor, the results of several analyzes are necessary:
- L"symptom analysis it's a"anamnesis accurate can provide the first indications on the location of the primary tumor;
- Laboratory tests, provide information on how the tumor affects the normal functioning of the body;
- Diagnostic for images (X-rays, CT, magnetic resonance, etc ...), allow to determine the "extension of the tumor and the presence and localization of a" possible metastasis;
- Percutaneous biopsies or endoscopic, with these techniques a part of the tissue affected by the tumor is taken and the cells that compose it are analyzed, thus allowing to identify the nature of the tumor.
